power surging at cruise speeds

Hey guys, been reading for a while and now have a question.  I have a 73 4-speed coupe that I just finished an engine swap and now have a couple of issues.  I put in a new GMPP 290HP 350 long block with Edelbrock performer intake and a Holley 670 Street Avenger carb.  I also switched to a HEI ignition set up with the gear driven tach.  My exhaust is Headman headers and the under car chambered exhaust from MA motorworks.  The car is now complete and I am trying to tune it in just right.  The car is hard to start when cold, sometimes and other times starts right up.  It also has a very noticible surg at cruising speeds and on medium throttle accelerations.  The idle speed is also hard to set.  I can get the car warm and set it to 900, then after driving the car it will idle at 1500.  Every part on the engine is also brand new, nothing reused or salvaged.  Any advice you guys have would be very appreciated.  Thanks.

Sounds like a vacuum leak somewhere to me.  Check your vacuum take off to the headlight/wiper door system.  Manifold leak?  Power valve in the Holley?  Auto Choke? 

Chips is right where I was goin...sounds like a vac. leak to me, also.
It could also be an issue with the carb. Check to see that the linkage is functioning correctly, and will open fully, and close fully, with no "binding". Sometimes, the base gasket for the carb will have holes that are too small, or off-set a bit, and the throttle blades will hang/stick on it. Make sure the secondary throttle blades are closing completely.
I'd start by verifying there are no vacuum leaks, tho. That be what it sounds like.

Thanks for the advice guys.  I will check for leaks this evening.